// 参考 https://github.com/darknessomi/musicbox/wiki/
"use strict";
const crypto = require("crypto");
const bigInt = require("big-integer");
const modulus =
    "00e0b509f6259df8642dbc35662901477df22677ec152b5ff68ace615bb7b725152b3ab17a876aea8a5aa76d2e417629ec4ee341f56135fccf695280104e0312ecbda92557c93870114af6c9d05c4f7f0c3685b7a46bee255932575cce10b424d813cfe4875d3e82047b97ddef52741d546b8e289dc6935b3ece0462db0a22b8e7";
const nonce = "0CoJUm6Qyw8W8jud";
const pubKey = "010001";

String.prototype.hexEncode = function() {
    let hex, i;

    let result = "";
    for (i = 0; i < this.length; i++) {
        hex = this.charCodeAt(i).toString(16);
        result += ("" + hex).slice(-4);
    }
    return result;
};

function createSecretKey(size) {
    const keys =
        "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    let key = "";
    for (let i = 0; i < size; i++) {
        let pos = Math.random() * keys.length;
        pos = Math.floor(pos);
        key = key + keys.charAt(pos);
    }
    return key;
}

function aesEncrypt(text, secKey) {
    const _text = text;
    const lv = new Buffer("0102030405060708", "binary");
    const _secKey = new Buffer(secKey, "binary");
    const cipher = crypto.createCipheriv("AES-128-CBC", _secKey, lv);
    let encrypted = cipher.update(_text, "utf8", "base64");
    encrypted += cipher.final("base64");
    return encrypted;
}

function zfill(str, size) {
    while (str.length < size) str = "0" + str;
    return str;
}

function rsaEncrypt(text, pubKey, modulus) {
    const _text = text
        .split("")
        .reverse()
        .join("");
    const biText = bigInt(new Buffer(_text).toString("hex"), 16),
        biEx = bigInt(pubKey, 16),
        biMod = bigInt(modulus, 16),
        biRet = biText.modPow(biEx, biMod);
    return zfill(biRet.toString(16), 256);
}

function Encrypt(obj) {
    const text = JSON.stringify(obj);
    const secKey = createSecretKey(16);
    const encText = aesEncrypt(aesEncrypt(text, nonce), secKey);
    const encSecKey = rsaEncrypt(secKey, pubKey, modulus);
    return {
        params: encText,
        encSecKey: encSecKey
    };
}

module.exports = Encrypt;
